Final answer:
A cell that has many mitochondria is highly active and requires a lot of energy.
Step-by-step explanation:
A cell that has many mitochondria can be inferred to be highly active and requires a lot of energy. Mitochondria are organelles responsible for producing ATP, which is used as the cell's energy source. Therefore, cells that need a high amount of energy, such as muscle cells, have a large number of mitochondria.